One of the problems with very small radios is the frequency readout. It’s important to know what frequency you are operating on. However, a dial mechanism that is big enough to display the operating frequency adds a lot of size to a rig and, if your goal is to make the rig as small as possible, a frequency display can be a problem. Also, if you try to use a frequency display with LED or liquid crystals for a digital display, these types of displays consume a LOT of power, defeating the goal of keeping the rig small so it can operate on battery power.
PIC-based Frequency Counter
Enter the PIC-based frequency counter with Morse code readout. A PIC is a “Programmable Interface Controller.” Basically, a PIC is a tiny computer on an integrated circuit. Here’s a photo of a PIC that I snipped from somewhere on the Internet.
The programming instruction set for PIC’s is limited but powerful. These devices are in everything — bread machines, microwave oven, vehicles, TV sets, DVD players — you name it.
A PIC-based frequency counter is used in a circuit that takes a small bit of signal from the rig to which it is attached. The signal is, or is converted to, digital data equal to the frequency to which the rig is tuned. The PIC is programmed to read that digital data then convert it to Morse code and send the Morse code to an attached speaker or headphone, or to inject the Morse code into the audio circuit of the rig to which is is attached.
The FreqMite — A PIC-based Frequency Counter
The answer is simple. Dave Benson of Small Wonder Labs — who makes the RockMite and the SW+ CW transceivers — makes a PIC-based frequency counter that he calls the FreqMite. Here’s a description from Dave’s website:
The ‘FREQ-Mite’ is a PIC-based Morse frequency counter measuring only 1.25″ x 1.75″ x 0.45″ (H) and is capable of operation to more than 30 Mhz. To get this compact size, frequency readout is in audio (Morse code) form .
When used in ‘transceiver’ mode, it outputs three Morse digits corresponding to frequency (hundreds/ tens/ units Khz). The FREQ-Mite is shorting-jumper programmable to any offset (0-999) and may be run in either normal or inverted (high IF) readout. It can also be configured as a general-purpose counter, and in this mode outputs 4 or 5 digits up to a maximum of 32.767 Mhz. The RF input is high-impedance and requires a minimum of less than 200 mV p-p up to 10 Mhz and under 600 mV p-p at 30+ Mhz. Accuracy is +/- 1.5 Khz to 25 Mhz and +/- 2 Khz at the high end. It’s activated by pressing a pushbutton switch, and enters ‘SLEEP’ mode when not in use to preclude receiver interference.
The default speed readout on the FREQ-Mite is 13 WPM, but a fast (26 WPM) mode may be selected upon power-up. The output is an 800 Hz tone; this signal is tri-stated off when not in use to minimize ‘thump’. The output is capable of driving an “external-drive” type Piezo annunciator or speaker/headphones directly at modest audio levels. It really shines, though,when installed into a QRP transceiver to augment whatever dial-marking scheme you’ve been living with until now.
The FREQ-Mite uses a high-quality double-sided PC board, which is solder-masked on both sides and silkscreened. The kit provides all on-board parts, interconnect wire, mounting hardware and a comprehensive 6-page set of instructions.
So — the FreqMite is a tiny PC board frequency counter that attaches to any rig. The FreqMite (FM) taps a small RF signal from the rig’s VFO, reads the frequency, applies an offset equal to the IF frequency ( if needed ), and sends the frequency in a three-digit Morse code signal that can be attached to the rig’s audio line so you hear the operating frequency sent in Morse.
For example, if I am on 7.039, when I press the button that activates the FreqMite , I hear in the headphones Morse code “0 3 9.”
Configuring the FreqMite to work with the Small Wonder Labs SW-series transceivers
Here is a hook-up diagram photograph. Look at the bottom right of the photo, between ACTIVATION SWITCH and GND — the double row of pins sticking up is J1 — these are the jumpers that are used to configure the FreqMite to read the frequency of your rig. The kit comes with ten jumpers that are inserted over sets of these pins as described in the setup instructions that come with the FreqMite. Read further to see how to configure the jumpers for the SW-40 and SW-80.
I have installed a FreqMite in my SW-40 and SW-80 QRP CW transceivers. Here is how I did it.
|AF OUT||Top of R9. May need to insert as much as 100K resistor in series to reduce audio output.|
|Ground||Ground to chassis and to SW- board|
|V +||Any source of 7-15 VDC; SW rig power|
|RF||Top of R17 — connect to “FROM VFO” in the diagram above”|
|S1||Normally OPEN push-button switch (ACTIVATION SWITCH)|
Setting the jumpers: The FreqMite J1 has ten sets of jumpers used to configure the FreqMite to measure the rig’s operating frequency. I have installed a FreqMite in only the SW-40 (40 meters) and the SW-80 (80 meters)
SW-40: DO NOT INSTALL ANY JUMPERS ON J1.
Number Jumper – ? 1 Yes 2 Yes 3 Yes 4 Yes 5 Yes 6 No 7 No 8 Yes 9 No 10 No
When you power up the SW rig with the FreqMite installed, the FreqMite sends three CW messages — this is how to respond to those messages.
|S||On both the SW-40 and SW-80, if you press S1 within 2 seconds, FreqMite will send at 26 WPM. If you do nothing, FreqMite sends at 13 WPM (the default setting)|
|I||Invert? SW-40: Do not press S1 — do nothing — listen for AR.||Invert? SW-80: PRESS S1. Listen for AR.
|AR||SW-40 and SW-80: Do nothing. No response required. Ready to operate.|
Where can you buy the FreqMite kit?
For several years, the FreqMite was produced by Small Wonder Labs, owned and operated by Dave Benson,
In November 2013, Dave Benson shut down Small Wonder Labs. Dave had been designing and selling QRP rigs since 1996. In 2013, he decided there was more to life than putting parts in little plastic bags. Dave shut down his website in November 2014.
Four States QRP Group has picked up production of the FreqMite. Their website has ordering information as well as links to photos, construction and operating manual, and the like.